Evolution and Endogenous Interactions

We examine an evolutionary model with "local interactions," so that some agents may be more likely to interact than others. We show that equilibrium strategy choices with given local interactions correspond to correlated equilibria of the underlying game, suggesting an new interpretation for correlated equilibrium. We then allow the pattern of interactions itself to be shaped by evolutionary pressures. If agents do not have the ability to avoid unwanted interactions, the heterogeneous outcomes can appear, including outcomes in which different groups play different Pareto ranked equilibria. If agents do have the ability to avoid undesired interaction, then we derive conditions under which outcomes must be not only homogeneous but efficient.